Generally, as shown in FIGS. 1 and 2, a turbocharger has a bearing housing 3 integrally arranged between turbine and compressor housings 1 and 2, a turbine shaft 5 being rotatably supported by the bearing housing 3 via a bearing portion 4. The turbine shaft 5 is provided on its one (front) side with an impeller 6 surrounded by the compressor housing 2 and on its other (rear) side with a turbine rotor 7 surrounded by the turbine housing 1.
The bearing portion 4 in the bearing housing 3 is composed of a thrust bearing comprising floating bushes 4a arranged as rotary bearings on the turbine shaft 5 and spaced apart from each other axially of the shaft 5, an inner plate 4b which restrict axial movement of the floating bush 4a, an outer thrust bracket 4c fixed in the bearing housing 3 via a bolt 8 and a thrust collar 4d arranged between the inner plate 4b and the outer thrust bracket 4c and abutting on a stepped portion 5a of the turbine shaft 5.
The bearing housing 3 is formed with a supply opening 9 directed toward the turbine shaft 5 and a first branch flow passage 10 branched from the opening 9 to the floating bush 4a, lubricant fed to the opening 9 being supplied via the flow passage 10 to between the bush 4a and the housing 3 and to between the bush 4a and the shaft 5, thereby forming oil films for support of rotation of the shaft 5. In this regard, for formation of the oil film between the bush 4a and shaft 5, the floating bush 4a is formed with an oil passage 11 diametrically passing through the bush 4a. 
The bearing housing 3 is further formed with a separate second branch flow passage 12 branched from the opening 9, lubricant fed to the opening 9 being supplied via the flow passage 12 and an oil passage 13 in the outer thrust bracket 4c to between the bracket 4c and thrust collar 4d for formation of oil film to receive thrust load.
Arranged at an outer periphery of the turbine shaft 5 and between the thrust collar 4d of the bearing portion 4 and the impeller 6 is a tubular oil thrower 14 which has a front portion 14a formed at its outer periphery with an annular groove 14b receiving a piston-ring-like seal ring 15. The oil thrower 14 has a rear portion 14c fitted in an inner periphery of the outer thrust bracket 4c with a slight gap 16.
Arranged to face the outer periphery of the front portion 14a of the oil thrower 14 is a seal plate 18 fixed via a bolt 17 to the bearing housing 3, the piston-ring-like seal ring 15 in the groove 14b of the oil thrower 14 abutting on an inner periphery of the seal plate 18 by its expansive spring force. The seal plate 18 is positioned at a back of the impeller 6, is sized to be greater than an outer diameter of the impeller 6 and provides a part of a flow passage 20 on a diffuser 19 for flow straightening of compressed air from the compressor.
When such turbocharger is driven, the turbine rotor 7 is rotated for example by exhaust gas from the engine, the impeller 6 being driven by the rotated turbine shaft 5 to suck and compress air via a suction port 21. The compressed air is flow-straightened by the flow passage 20 of the diffuser 19 and is supercharged into the downstream engine for enhanced output performance of the engine (see, for example, Reference 1).
In this case, when lubricant is supplied via the supply opening 9 to the bearing portion 4, oil films are formed between the floating bush 4a and bearing housing 3 and between the floating bush 4a and turbine shaft 5; the lubricant having formed the oil films is flowed out via a gap between the inner plate 4b and turbine shaft 5 and via a gap between the inner plate 4b and thrust collar 4d. Lubricant is also supplied to between the outer thrust bracket 4c and thrust collar 4d for formation of oil film; the lubricant having formed the oil film is flowed out via the gap 16 between the rear portion 14c of the oil thrower 14 and the outer thrust bracket 4c. 
[Reference 1] JP 2002-38966A